The pollution from human activities has now reached the deepest trenches of the ocean. Accumulated toxic chemicals can be found in marine creatures in such depths.

By now, it was considered that deep-sea trenches were remote enough and untouched by mankind influence. That was stated by Alan Jamieson, a deep-ocean scientist from the University of Aberdeen in the United Kingdom. But now Jamieson and the other members of the team found man-made organic pollutants in the depths. Such chemicals were discovered at high levels in shrimp-like crustaceans known as amphipods. The scientists collected them from two deep-ocean trenches.

Before this research, such data was quite limited – for species that live at the ocean depths of 2,000 meters or less. The newest research was checking the levels of organic chemicals in amphipods collected at 7,000–10,000 meters depth. They were taken from the Mariana Trench, located in the western Pacific Ocean, as well as the Kermadec Trench, located near New Zealand.

The ocean creatures were collected during 2 international expeditions in 2014. Then, the researchers lowered landers into the trenches. This was a part of a research program which will study deep-ocean ecosystems. The program is sponsored by the US National Science Foundation.

Mankind Pollution in the Ocean

In the samples from both trenches, the scientists found amphipods which contained polychlorinated biphenyls (PCBs). These chemicals are used to make plastics. Polybrominated diphenyl ethers (PBDEs) were also found in the samples. These chemicals are used as flame retardants.

These man-made chemicals belong to a category of carbon-based compounds known as persistent organic pollutants (POPs). They are called ‘persistent’ because they are quite hard to break down. The production of such chemicals which are known to be carcinogens, has been banned by numerous countries since the end of the 1970s. PBDEs are suspected to disrupt hormone systems and interfere negatively with neural development.

It is definitely a quite bad news that such chemicals were found in the ocean depths. The concentrations of the PCBs in the collected amphipods from the Mariana Trench were surprisingly high. These levels were 15 times greater than the ones from the Kermadec. On the other side, in the Kermadec Trench the PBDEs concentrations are five times greater than in the Mariana Trench.

Douglas Bartlett, a microbiologist from the the Scripps Institution of Oceanography in San Diego, California, states that the discovery is stunning. According to him the findings prove that the trenches are not actually so remote and everything in the world is connected.

The scientists consider that the proximity of the Mariana Trench to big plastic Asian manufacturers and to a long-term US military base on the island of Guam may be closely connected with the high PCB levels. Also, the waters above the trench are part of the North Pacific gyre. This is a system of strong swirling ocean currents which take materials from the surface down into the deep sea. Both the Kermadec and the Mariana trenches are about 11 kilometers deep.  But it is obviously not deep enough for man-made pollutants.